Structure and reactivity in reactions of dimethyltin(IV) di(azide) and di(isocyanate) with dimethylplatinum(II) complexes

Abstract

In situ reaction of SnMe₂Cl₂ with NaN₃ or KOCN in methanol or a mixture of acetone/H₂O solution has resulted in the formation of SnMe₂(N₃)₂ (1a) and SnMe₂(NCO)₂ (1b) complexes, respectively. The reaction of dimethylplatinum(II) complexes [PtMe₂(NN)], NN = bpy (bpy = 2,2′-bipyridine) or 4,4′-Me₂bpy (4,4′-Me₂bpy = 4,4′-dimethyl-2,2′-dipyridine), with 1a or 1b occurs initially by oxidative addition but the initial platinum(IV) products [PtXMe₂(SnMe₂X)(NN)], decompose during attempted isolation to give new organoplatinum(II)/(IV) complexes that contain Pt-N₃ or Pt-NCO bonds, several of which were characterized crystallographically. The reaction of electron-rich complex [PtMe₂(bpy)] (bpy = 2,2′-bipyridine) with 1a resulted in the formation of the new Pt(IV) complex fac-[PtMe₃(N₃)(bpy)] (2). However, the similar reaction of 1a or 1b with [PtMe₂(4,4′-Me₂bpy)] (4,4′-Me₂bpy = 4,4′-dimethyl-2,2′-dipyridine) gave the corresponding Pt(II) complexes [PtMe(N₃)(4,4′-Me₂bpy)] (3), or [PtMe(NCO)(4,4′-Me₂bpy)] (4), respectively. The reaction of [PtMe₂(4,4′-Me₂bpy)] or [PtMe₂(bpy)] with SnMe₂Cl₂, followed by addition of KOCN, gave [PtCl₂(4,4′-Me₂bpy)] (5) or fac-[PtMe₃Cl(bpy)] (6), respectively. The crystal architecture in compounds 2–4 and 6 is stabilized by weak hydrogen bonds and π···π interactions. Further insight was obtained by monitoring the reactions in situ using multinuclear (¹H, ¹³C, ¹¹⁹Sn, ¹⁹⁵Pt) NMR spectroscopy in different solvents and by DFT calculations.